1. Field of the Invention
The present invention relates to a hybrid integrated circuit device and, more particularly, to a hybrid integrated circuit device which is improved to make it possible to fully utilize the output performance of a component of the device.
2. Description of the Related Art
Referring to FIG. 5 which is a sectional side elevational view of a known hybrid integrated circuit device, an aluminum insulating substrate 2 is fixed to the upper side of a secondary heat sink such as an alumina heat sink 1 by soldering as at 3. A primary heat sink such as a copper heat sink 4 and a heat-generating semiconductor chip such as power transistor 5 are mounted successively on the aluminum insulating substrate 2 by soldering as at 3", 3'3. A thick film resistor substrate 7 is fixed to the aluminum heat sink 1 by an adhesive 6 such as a silicone resin type adhesive. Circuit elements such as conductors 8 and resistors 9 are formed on the thick film resistor substrate 7 by, for example, printing, and other circuit elements such as capacitors 10 and a controlling IC are fixed to the upper side of the thick film resistor substrate 7 by soldering as at 12. The power transistor 5 is electrically connected to the thick film resistor substrate 7 through, for example, a wire such as aluminum wire 13.
In the known hybrid integrated circuit having the described construction, the power transistor generates heat at a large rate. In order to prevent breakdown of the hybrid integrated circuit device, therefore, it is necessary to maintain the temperature of the hybrid integrated circuit device during operation at a temperature below the lowest bonding temperature in the device. Hitherto, such temperature control has been achieved by tentatively cutting off the power supply or reducing the level of the power so as to maintain the temperature of the hybrid integrated circuit device within a predetermined range of temperature. More specifically, the known hybrid integrated circuit device has a temperature measuring means (not shown) provided on the aluminum heat sink 1 which serves as the secondary heat sink, and the power applied to the device is controlled in accordance with the temperature measured by the temperature measuring means, to thereby maintain the temperature of the device below the lowest bonding temperature.
In this known hybrid integrated circuit device, however, it is impossible to accurately measure the temperature of the device because the temperature measuring means is provided on the aluminum heat sink 1 which serves as the secondary heat sink. Consequently, it has been impossible to make the full use of the output performance of the hybrid integrated circuit device.
Thus, the thermal design of the hybrid integrated circuit device has to have a large margin, and the power supplied to the device has to be carefully controlled to prevent any portion of the device from being heated to a temperature above the minimum bonding temperature. As a consequence, the potential output performance of the hybrid integrated circuit device could not be fully utilized.